Hertz (and Thrifty) are just outside the airport north entrance.
After you pick up your car, you come out onto the main drag (436; Semoran). Then right at the last light in sight (Frontage becomes McCoy), a little over a mile, west, is the next light (Conway), Left and instantly another left to get on 528 (Beach Line; Bee Line) west to I-4 west (southwest) to Disney. Exact change not mandatory for the toll booth.
Returning via I-4 East (northeast) to 528 East, get off 528 at its exit 9 (Tradeport/Conway), left and cross under * and get into middle lane. Required right onto McCoy, then next light a mile or so east is Semoran and go left to return the car.
* Nice cheap gas station right there to top off at.
Disney hints:
http://members.aol.com/ajaynejr/disney.htm